Turn 4 Assistance

[Royal]

My FC and I have been struggling with Turn 4, specifically Wave 6. I was wondering if someone has any insight. Our group composition is 2 tanks, 2 healers (WHM/SCH), 2 melee dps (bard/drg), and 2 BLM.

We have entered Wave 6 multiple times with the single dreadnaught alive ranging from 55% to 70ish%. I realize he should be a little lower but that isn't our problem (yet!). The last wave spawns 1 soldier, 1 knight, 1 rook, 2 bugs, and another dreadnaught if memory serves me right.

Here is what we've been doing. At the start of Wave 6, we immediately blow up the spinner rook to prevent any unwanted pox applications and is usually tanked by a melee dps (drg). He handles it fine at first but usually one of the BLMs will steal aggro pretty quickly and manawall tank it. It does not take very long to die at all.

The MT picks up the 2nd dreadnaught who was already tanking the first dreadnaught from Wave 5.

The OT picks up the soldier, knight, 2 bugs all on himself and immediately does hallowed ground. Everything goes perfectly fine until hallowed ground disappears and then he just drops. If i remember correctly, the rook dies about the time his hallowed ground disappears. After I help finish the rook all dps goes on the old dreadnaught. This is our wall. The rook is dead, the Wave 5 dreadnaught is pretty close to where he should be in terms of dps (~50%), and everything is controlled aggro wise at least, nothing is running around. I do not think the problem is healing to be honest, I think it is a mechancial problem. A flaw in our strat but we can't figure it out.

Our average gear level is 3-5 ilvl 90s and very little if none of the HQ crafted items. Our dps is pretty good I feel. We cleared Wave 3 dreadnaught with ease everytime. I mention the gear just in case you guys think that is the problem.

Any help would be greatly appreciated. Thank you for your time.

EDIT: A big point of discussion has been what to LB at this point. We can't decide.